[Gta04-owner] [Community] GTA04 power management [was: About cost and business models for community hardware]

H. Nikolaus Schaller hns at goldelico.com
Tue Sep 29 10:33:36 CEST 2015

Hi Neil,

Am 29.09.2015 um 02:45 schrieb Neil Brown <neilb at suse.de>:

> "H. Nikolaus Schaller" <hns at goldelico.com> writes:
>>> I think Radek ‘lost interest' because of lack of some of the lower level points in my list above, principally the battery consumption.
> Battery consumption is the main issue that depresses my enthusiasm.
> It *seems* insoluble.  It probably isn't, but I haven't found a way
> forward.

I think we should address it a little more analytically.

IMHO we have two problems with more modern kernels:
* they do not yet have all features (e.g. we are still lacking e.g. hardware voice routing and some other features)
* device tree and CPU power management has changed significantly - and faster than we can understand the changes

Therefore we have no stable basis ("all features work") to optimize power.

Regarding power saving I think we have to address:
* all peripherals are properly turned off in power-down mode
* RAM is in self refresh
* CPU is sleeping in lowest possible state
* until a call is coming in, a button is pressed or USB power is plugged in

So which parts are not working well?
Is this related to our code or to CPU core driver?
How (well) does the N900 (RX51) mainline code handle this?

>> Well, with 3.7 it was almost good.
> I would say 3.7 is just barely usable - if you have a new battery.
>> A problem for me is that QtMoko has some very nice tools to support battery consumption measurements. But because it does neither run on 3.12 or later kernels, we can’t even test battery consumption easily. How to improve the kernel if a good GUI is missing.
> Measuring battery usage isn't that hard.  In the simplest case you just
> need to log the time (seconds) and the charge-now value from the
> bq27000 and graph those.  I log them on every 'suspend' and 'resume' so I
> can easily get data.

Yes, there are other techniques, but QtMoko already provides such tools.

> I find it a bit harder at present because all of my batteries with
> bq27000 in them have died.

Oops. How does this come? I now have the first of several that appears
to have a problem (charges within short time and is then empty...).

>  I've got a Nokia BL-5C in my phone at the
> moment.
> I ripped the bq27000 board off one of the dead batteries and managed to
> attach it to another BL-5C so I can do measurements, but only on my old
> "spare" board (which has lost its USB connector so I need WIFI for all
> networking...)

For the GTA04A5 board there will be an additional bq27621 chip on the main
board to measure battery status. So even a battery w/o bq27000 can be measured.
But I don't know the precision.

> If I could even get current mainline down to 3.7 power usage levels I'd
> probably be motivated to keep working on upstreaming things, but I've
> hit a brick all there too.

The question is in which subsystem the problem is located? Where do
you hit bricks? What is not working as you expect?

Probably we should discuss more about such issues and help
each other instead of individually trying to run against walls in small
black boxes.


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